Worm-gear.



F. K. FASSETT.

WORM GEAR.

APPLICATION FILEDFEB. s. 1913.

Patenea 0015.6, 1914.

' subsequent wear.

FRANCIS K. FASSETT, 0F DAYTON, OHIO.

WORM-GEAR.

Specification of Letters Patent.

. Patented Oct. 6, 1914.

Application filed February s, 1913, Serial No. 745,845.

To all whom it may concern:

Be it known that I, FRANCIS K. Fnssn'rr, a citizen of the United States,residing at Dayton, in the county of Montgomery and State of Ohio, haveinvented a new and usei ful Improvement in \Vorm-Gears, of which thefollowing is a specification.

My invention relates to worm-gears and has for its principal 0b]80t toprevent lost motion, or what is commonly called backlash, in worm-gears.

Another object is to so construct wormgears that as the parts wear, theback-lash resulting therefrom may be taken up.

Another object is to alter worm-gears of a certain type in such mannerthat though they are so badly worn as to be unfit for use in theiroriginal form they" may, when altered, be restored to their formereffectiveness, and operated as long, or longer, after said alteration,and with more satisfactory results than were attained during) thegreater part of the time they were used efore being altered.

There are two kinds of worm-gears: single and double. The former is asingle worm enmeshed with a. single gear wheel. The latter comprises twoworms, one right and one left hand, rigidly secured to a single shaft,and two cars enmeshed with each other, one gear eing also enmeshed witheach worm. Both kinds of worm-gears are liable, in fact likely, to havemore or less back-lash, due to original poor fitting or This is aserious defect, especially where the gears are used in elevators, forwhich service worm-gears have come into quite general use. Doublewormgears have one advantage over single ones:

They do not require thrust hearings to revent longitudinal movement ofthe sha t as single worms do; each worm of the double ear acts as athrust bearing for the other.

lines roller and ball thrust bearings have reached their present stateof dove opment this is not, however, as much of an advantage asformerly. My method of reventin back-lash will how be explaine i ure 1represents a double worm gear, and ig. 2 a thrust bearing or step. Theworms and gears in Fig. 1 are presumed to have been worn considerably.

Operating as a normal double-worm gear,

without the step 8 ahd with the shaft rotat- 55 ing in the directionindicated by the spiral arrow, the worms wouldltend to'separate'thesimultaneously drive gear 5.

lower parts of the gears; z. 6., move them in the direction of theirarrows. connected to the drum, which it is presumed would not moveuntilforoed-to, the worm 3, e(

and hence the shaft 1 and worm 2, would when rotated move'longitudinallytoward the gear 4. This longitudinal movement of the worm 2, togetherwith its rotary movement, would rotate the gear .4 in the direc- 65 tionof its arrow and bring its teethinto contact with those of the gear 5.The longitudinal movement of the shaft would then cease and rotation ofgear'5 begin. Be-

versing the direction of shaft 1, the gear 5 7 again remainingstationary until forced to move, the-shaft would move to'theleft,:r0-

tating the gear as before but in the other. direction, until its teethengaged thosev of gear 5 after which the latter wouldbgin 75 to rotate.It is clear therefore that .each

time'the direction of rotation of theshaft 1 occurred it would rotate tosome extent. and move longitudinally some distance :before the. gear 5would start to rotate.-:.-..The 0 amountoflost motion would, of'course,depend upon the condition of the parts, but my invention will eliminateall lost motion as will now be explained.

It will be understood that the sha f t; and

gears arc'provided with bearings carried bya suitable supporting frame,and the step 8 is mounted in an arm carried by the'same frame. By meansof the nuts the step may be made to push the shaft longitudinally to theright as far as possiblethe limit of its movement being reached when theworms, actin as racks, have rotated both gears in the lrection of thearrow on gear 4 until their teeth engage at 6. This may be done with theworm shaft rotating or still, but preferably the latter. Securing thestep, I have this condition: The right side of each worm is lyingagainst the teeth of its gear. See Fig. 1. If the shaft be rotated inthe direction indicated by the s iral arrow the worm 2 will immediatelyrive gear 4 in the direction of its arrow and gear 4 will As the rightside of worm 3 is lying against the teeth of its gear, it is clear thatthere will be a space between the left side of the worm and the teeth asshown in the drawing. Therefore, worm 3 will not drive gear 5. Roversingthe direction of rotation :since the right s1 e of worm 3 is alread incontact with the teeth of gear 5 it will immediately drive Gear 5 beinggear 5.. But worm 2 will notdrive gear 4;

thisfor the same reason worm 3 did not longitudinal thrust on the wormshaft is in the same direction whichever way it rotates,

and for this reason the step 8 need be at one end only. "Notwithstandingthis independence of action there is a certain inter-dependencebetweenthe parts, namely: when the shaft is rotating in the direction indicatedby the arrow gear 5 depends upon ear 4 for its propulsion, and the wormsha t is prevented from moving longitudinally to the right by theinterlocking of gears 4 and 5. 1 v

Instead of step 8, a ball thrust hearing may be used. Figi 2 shows abearing of this type incased in a 'ousing built out fiom the s aftbearing 9. 7 The inner wall of the housing,-w hich is cylindrical, isthreaded to receive the threaded disk 10. This disk, be-

ing provided with spanner wrench holes 11, a slot 12 and clamping screw13, may be screwed in, pushing the shaft 1' as far as is necessary totake up all back-lash in the gear, after which the screw 13 is drawn uptight to clamp the disk inplace.

. A worm-gear of this type has decided advantages over any other form ofworm-gear. Equipped with a ball or roller thrust hearing it has theefficiency of the best single worm-gear, and since one worm drives thedrum in one direction and the other worm drives it in the otherdirection it has the durability of the double ,worm-gear. Because of theinterlocking action of the gears the parts ay be'ke'pt entirely freefrom backlash; this eliminates the noise, and what is far worse, thejarring of the machine. A double worm-gear vhose parts have become sobadly worn that they cannot be used, may, by putting on-the thrusthearing, be converted into this form of gear. When so altered the partsmay be used as long as they were used before the conversion, possiblylonger, and all that time operate more quietly and satisfactorily thanthe gear operat'ed durin three-fourths of its period of use as a dou legear. The mere saving of money which may thereby be effected is quite anitem, as the cost of converting a gear w1ll probably not exceedone-third of the cost of ,gienewing the parts.

What I claim is as follows:

1. The combination of a worm-gear comprising two toothed wheelsrotatably mounted with their teeth enmeshed and a pair of worms mountedupon a common shaft with one worm engaging each wheel, and a thrustbearing adapted to prevent longitudinal movement of the shaft in onedirection.

2. The combination of a worm-geareomprising two toothed wheels rotatablymounted with their teeth enmeshed and a pair of worms mounted upon acommon shaft with one worm engaging each wheel, and a thrust bearingadapted to push the shaft longi't'fi dinally as far as the worms andteethwill permit.

3. The combination of a worm-gear comprisin two toothed wheelsrotatablymounted wit their teeth enmeshed and a pair of ,worms, oneright hand and the other left hand, mounted upon a common shaft with oneworm engaging each wheel, and a thrust bearing to hold the shaft in suchposition. longitudinally that when it rotates in one direction only onewheel is driven by its worm and when rotated in the'opposit-e directiononly the other wheel-is driven by its worm.

4. A worm-gear comprising a shaft with a right-hand'and a left-hand wormrigidly secured thereto, a pair of gear wheels having their teethenmeshed with each other,- one of the gears being also enmeshed witheach worm, and a thrust bearing where y the shaft may be movedlongitudinally and 1 held me position where the interlockmg'of the gearsprevents further longitud nal movement thereof. V

5. A worm-gear comprising a shaft with a right-hand and a left-hand wormri idly secured thereto, a pair of gear wheels av- 10 ing their teethenmeshed with each other, one of the gears being also enmeshgdq witheach worm, and a thrust bearin 'wliereby the shaft may be movedlongitudinally andheld in a position where the worms are pre- 101 ventedfrom acting simultaneously to drive their respective gears.

6. The combination of a worm-gear having a worm carrying shaft adaptedto rotate in either direction, and means whereby the longitudinal thrustof the shaft is'in the same direction whichever way it rotates.

7. The combination of a worm-gear comprising two toothed wheelsrotatably mount cd with their teeth enmeshed and'a air of 11 wormsmounted upon a common sha t with one worm engaging each wheel, and meansadapted to cooperate with the worms and teeth to preventlongitudinalmovement of the shaft. 12

8. The combination of aworm-gear, comprising two toothed wheelsrotatably mounted with their teeth enmeshed and a air of worms mountedupon a common sha t'with one worm enga ing each wheel, and a thrust 1bearing adapted to positively push the shaft longitudinally as far asthe worm and teeth will permit.

9. A worm-gear comp'risin a shaft with a right-hand and a'left-han wormrigidly 11 secure uiemtu, a pan of gear wheelshaving their teethenmeshed with each other, one of the gears being also enmeshed with eachWorm, and a thrust bearing whereby" the shaft may be positively movedlongitudinally and held in a position where the interlocking of thegears prevents further'longitudinal movement thereof.

10. A worm-gear comprising a, shaft-with a right-hand and a left-handworm rigidly secured thereto, a pair of gear wheels having their teethenmeshed with each other, one of the gears being also enmeshed with eachworm, and a thrust bearing whereby I the shaft may be positively movedlongitu C. HIKRUGER, J. A WORTMAN.

